Effect: The magician shows you two decks of cards, one red backed and one blue backed. The magician explains that his cards are highly adaptive and he'll show you what he means. He places the blue backed cards in the red card box and the red backed cards in the blue card box. He snaps his fingers over the two card boxes. Lo and behold, when he removes the cards from the red card deck, all the backs are RED! He takes the cards out of the blue deck and... all the backs are BLUE!

Procedure:

1. Before performing, get two decks of cards, one with all red backs and one with
all blue backs. take one card from the blue deck, preferably a joker, or some other
card you wouldn't often need and place it on top of the red deck. Then take one card
from the red deck, also one you wouldn't often need, and place it on top of the blue
deck. (see pic) You're ready.

2. show them one of the deck's back, but dont fan the cards. 97% of the time they
will assume it is a normal deck of cards with nothing out of the ordinary about it.

3. Place the deck you just showed them in an empty card box (for a better effect,
place the red deck with the blue top in a red card box and the blue deck with the red
top in a blue box.. repeat steps 2-3 with
the other deck.

4. Now, close the boxes and explain to them that the decks will magically change colors. If you put the red deck with the blue top in a red card box and the blue deck
with the red top in a blue box, you can explain to them that your two decks of cards
are highly adaptive and will change colours according to their box.

5. After explaining the above, snap, wave your hands over the deck, or your own style
of magical gesture. then open the deck, and make sure that the largest flap is closer
to the spectator. Take out the deck, but leave behind the top card. Repeat with the
other deck. you can fan the cards to show them that they are surely all one
color. Very simple method, great results.

A better way to do this is to get double sided tape and place it on the top card of each deck (the blue one on the red deck and the red one on the blue deck) Then you can just dump the cards out of the deck whilst the indifferent card gets left behind. The tape is usually clear enough that they don't notice. Use this variation at your own risk.